# Yellow Fever Virus (YFV) Detection in Different Species of Culicids Collected During an Outbreak in Southeastern Brazil, 2016–2019

## TL;DR

This study found yellow fever virus in multiple mosquito species during an outbreak in Brazil, raising concerns about potential urban spread.

## Contribution

The detection of YFV in various mosquito species, including non-primary vectors, highlights new transmission risks.

## Key findings

- YFV was detected in 1.4% of 3731 mosquito pools across nine species.
- Viral loads varied among species, with Aedes aegypti testing negative.
- Infection in non-primary vectors raises concerns about reurbanization of YFV.

## Abstract

Yellow fever virus (YFV) is an endemic arbovirus in parts of Africa and the Americas. In Brazil, following the eradication of the urban transmission cycle, YFV is maintained in a sylvatic cycle involving several species of neotropical primates and mosquitoes of the genera Haemagogus and Sabethes, which serve as primary and secondary vectors, respectively. During the 2016–2019 outbreak in São Paulo State, a total of 3731 mosquito pools were collected from sites with ongoing epizootic events in 192 municipalities. The RT-qPCR analysis detected YFV in 46 pools (1.4%) across nine mosquito species, including both primary and secondary vectors, as well as species from the genera Aedes and Psorophora. Differences in viral loads were observed among species. While Aedes aegypti was not found to be positive, the detection of natural YFV infection in other Aedes species raises concerns about potential virus reurbanization. Further studies are needed to clarify the role of additional mosquito species in YFV transmission in Brazil.